Pest Control in the Orchard Andrew Hewitt, Director Centre for Pesticide Application and Safety, University of Queensland, Australia and Research Professor The University of Nebraska, USA; Adjunct Prof., Lincoln University, NZ Geoff Furness, Mark Ledebuhr, Chris O Donnell, SARDI, AI, UQ
Thanks To Australian industry: Apple and Pear Australia Ltd, AGWA, others International: UQ, SARDI, Application Insight, HortResearch, PGG Wrightson and Pipfruit NZ, many others
Black Spot/ Apple Scab Fungal spores (e.g. from leaf litter) can cause leaf infection any time from bud break to full bloom. Infection is related to the length of continuous leaf wetness and ambient temperature, from 5 hours above 25 C to 20 hours at 6 C hence biological prediction based on weather forecasts and irrigation to avoid prolonged contact wetting Prevention depends mostly on successful fungicide applications to prevent primary infections in spring
Gloeosporium and other Rots Fungal disease typically seen during storage Cultural control (if practical) involves pruning and removing cankers during winter, and new cankers on limbs and trunks in spring/ summer as well as 1-year old shoots that wilt or die in spring/ summer. Minimize low hanging fruit late season Calcium sprays improve fruit resistance Chemicals like Captan if rainy periods occur prior to harvest but not within 7 days of harvest. E.g. 2 applns. of Mizar before its 28-35 day cutoff; then Captan 14 days before harvest; Pristine at 100% bloom/ petal fall (Gary Speers, PGG Wrightson, NZ)
PipFruit NZ/ HortResearch Study
Fungicides Protectant before spores land on leaves (use weather forecasts and apply before infection occurs) e.g. Dodine Pyrimidines Strobilurins azoxystrobin, fenamidone, kresoxim methyl, fluoxastrobin, pyraclostrobin, trifloxystrobin Dithiocarbamates metiram, mancozeb, thiram, mizar Curative after infection occurs, for up to 5 days post-rain e.g. DMI group
Organic Fungicides Potassium bicarbamate Copper or Bordeaux mixture early in season such as around budburst (limited effectiveness) Wettable sulfur Mineral/ neem oils Natural phenols/ phytoalexins
Genetic resistance Over a dozen genes have been isolated in apple cultivars that offer resistance to fungal diseases Just as pests evolve to provide challenges to their control, we can adapt by selecting optimized genetics along with customized pesticide and application systems
Tolerances Maximum Residue Levels/ Limits (MRLs) in fruit (and sometimes in pomace) Vary according to country of use, e.g. Boscalid 2-3 mg/kg Pyraclostrobin 0.5 mg/kg Captan 3-25 mg/kg Diothiocarbamates 0.5-10 mg/kg Dodine 0.9-5 mg/kg Strobilurins 0.1-5 mg/kg Pyrimidines, e.g. fenarimol 0.2-1 mg/kg
Apple and Pear AU Website MRL Table http://apal.org.au/wp-content/uploads/2013/04/apple-and-pear-mrls-september-2014.pdf
European Food Safety Authority Bases MRLs on properties of the ag product and good ag practices to ensure lowest possible human exposure (Reg EC396/2005) Risk assessment based on consumer intake being less than the toxicological ref value for each active Annual reporting of residues for >800 pesticides from >60,000 food samples across Europe and >15,000,000 member state measurements
Fungicide Resistance Plans Sterol inhibitors, pstrobilurins and others affected while contact fungicides are less affected Diodine less than 7 applications per season; less than 4 in sequence Pyrimidines less than 5 applications per season Strobilurins less than 4 applications per season DMI fungicides less than 5 applications/ season; always in a cocktail with protectants
Loss of Chemicals other than through Resistance De-registration, e.g. Benzimidazole not allowed in many countries due to Benzene content; some adjuvants restricted due to alleged toxicity (this is always a threat, even with the most widely accepted pesticides) Risk assessment involves assessing exposure, dose and toxicity need to address all these to maintain use Increasing restrictions on purchasing such as quality assurance schemes, sprayer testing schemes and auditing of produce from the tree to the supermarket shelves
Managing Pesticide Losses Many studies in tree crops have shown that more than half the applied chemical can be wasted on the ground and in airborne losses such as drift, rather than staying on the intended canopy Application technology, meteorological conditions, canopy and tank mix chemistry are all important Increasingly, countries are introducing restrictions on spraying but relaxing them if drift reduction technologies are used (Europe for decades and in 2015 the US, Canada and Australia as well as many others)
Spray fate in Orchards (Giles) Author Condition Ground Target Drift Seiber Dormant 25 45% - - Cross Both 43-63% - 16% Vercruysse Both - 56 68% - Pergher In season - 37 62% - Fox Sparse 57% - - Miller In season 22% 57% 4.6 (16%)
Optimized spraying of tree and vine crops Consider application rate on a distance/ height basis (e.g. 20-40 L/ 100 m per vertical canopy m) Do not spray above canopy top or below lower foliage Relatively fine sprays are needed for coverage (droplet size can be a major regulatory issue) + higher volumes than most other crop types and air-assistance is desirable for achieving penetration into the canopy and uniform coverage at all regions Calibrate sprayer and assess coverage, e.g. using fluorescent dyes/ UV light illumination looking at all canopy areas. Adjust as needed and repeat
80 to 120 60 to 90 40 to 60 20 to 30
Spray Volume Calculator (L/100m of row) l/min 3 km/h 4km/h 5km/h 6km/h 7km/h 8km/h 6 12 9 7.2 6 5.1 4.5 10 20 15 12 10 8.6 7.5 14 28 21 16.8 14 12 10.5 18 36 27 22 18 15 14 22 44 33 26 22 19 17 26 52 39 31 26 22 20 30 60 45 36 30 26 23
Other useful formulae: Length of row /hectare = 10 000 row spacing (m) Number of tanks required = total row length x spray volume volume of tank (m) (litres/100m) (litres) 100 Litres / hectare = litres / 100 m row spacing x 100
Sample leaves from all canopy areas and leaf regions Example of dye on grape leaves but apples would be assessed the same way
Alternative Assessment System using Kromekote and Image Analysis Black food dye on Kromekote, 4800 DPI scan, image analysis What you see (2 centimeter scan) What the computer sees:
Why hi-resolution image analysis? Tool to better understand what is going on DEEP in low-coverage areas. Understand and compare the areas of weakest application for better understanding of the overall application. Typical resolution scan, 100 DPI Hi-Resolution Scan of same 8 hits found 4800 DPI- 528 hits
Comparison of droplet spatial distribution between 2 machines- 2 cm scans in the least-covered areas (still hundreds of drops/cm 2 ) Multifan- typical low coverage area. Good spatial distribution, good overall coverage. Electrostatic- fewer measured hits but still good spatial distribution. Achieved with less than ¼ of the carrier water of the others. Polygons indicate the spatial distribution around each drop
Examples: DRT/ Total Environmental Load Reduction Systems Adjusting the spray dosage for the canopy prior to application, e.g. to spray to the first point of runoff only Adjust dosage to the canopy during appln., e.g. electronic eyes and sensors shown in US, China and Europe to reduce spray losses by ~50%. Dose adjustments can be achieved by turning nozzles on and off (e.g. PWM). Some sprayers capture, recycle and reapply spray that misses the canopy. Targeted air (e.g. converging airflow; towers; deflectors) Electrostatic charging under low wind speed and low evaporation conditions Tunnel and shielded sprayers Multi-row sprayers to apply rapidly while weather is optimal Spraying when wind is perpendicular to tree rows and not along the rows (this needs to be in context of the location of the sensitive area downwind)
Barrier Vegetation and Netting
Grapes <2m
Apples <4m
Almonds 8m
Pecans: 20m
Oranges: 4.5m, dense, small gaps
Grapefruit: dense; no gaps; raised beds
Dormant apple
Small grapefruit: 1.5m open spaces between trees
Developing New Lasers for Use in Field
Portable X-Ray Fluorescence In-situ (non-destructive and avoids need for artificial collectors with their own collection efficiency issues) Multiple cations can compare several sprayers under similar meteorological conditions Rapid processing (<1 minute per sample) Audit of spray deposition and coverage in field
Summary Managing diseases and pathogens in orchards while not exceeding off-target exposure, losses or residues and while avoiding resistance development requires careful consideration of cultural practices, pesticide application timing, equipment and tank mix choice Calibration/ dosing and auditing of spraying and spray performance can support optimized control without adverse impacts or over/ under-dosing